for the popwiated camp sites at Eniwetok. These, of course, were much less important factors at Bikini. For ‘SHOT/ an attempt was made to employ a method of el- liptical approximations of tne infinity iscdose lines on all fore- casts from about H minus 18 hours up threugh the final pre-shot forecast. This methed consisted cf circumscribing ellipses over the hcdograph between shear levels. As the Operaticn progressed, it became apparent that a more meticulous method was needed to clearly define the fallout from high yields, The elliptical ap- proximation methed, and any extension of the surface RADEX, beyond about six to twelve hours, were limited by the fact that they are built upon the ground zero winds. A new and dynamic method was needed to take into account the changes in the wind systems as particles drifted farther and farther from ground zerc. This resulted in a new technique develeped on CASTLE which utilized air particle trajectory analyzes and progressive forezasts of wind patterns in accordance with time and dispiacement aspects of the cleud. Prac- tical methods were devised to apply such a system to the last three CASTLE shots for a vaiid forecast period of H to H plus 24 hours. PART II RadSafeOrganizaticnforOperationCASTLE. A RadSafe Office waz Located in the Headquarters, JTF SEVEN, and this office had the ultimate responsibility for the CASTLE radiolegical safety program. During shct pericds, this office was designed to be the primary Task Force shot-time agency for all rad- = 254 = +